Possible high $T_c$ Superconductivity in La$_3$Ni$_2$O$_7$ under High Pressure through Manifestation of a Nearly-Half-Filled Bilayer Hubbard Model

TL;DR

This paper theoretically investigates high-pressure La$_3$Ni$_2$O$_7$ and suggests it can exhibit high-temperature superconductivity similar to a bilayer Hubbard model, despite some orbital coupling effects.

Contribution

It demonstrates that La$_3$Ni$_2$O$_7$ can host high-$T_c$ superconductivity modeled by a nearly-half-filled bilayer Hubbard system, providing a theoretical basis for experimental observations.

Findings

Superconductivity in La$_3$Ni$_2$O$_7$ is similar to the bilayer Hubbard model.

Coupling with $3d_{x^2-y^2}$ orbitals reduces $T_c$ but remains high.

High $T_c$ can be achieved despite orbital interactions.

Abstract

Inspired by a recent experiment showing that La$_3$Ni$_2$O$_7$ exhibits high $T_c$ superconductivity under high pressure, we theoretically revisit the possibility of superconductivity in this material. We find that superconductivity can take place which is essentially similar to that of the bilayer Hubbard model consisting of the Ni $3d_{3z^2-r^2}$ orbitals. Although the coupling with the $3d_{x^2-y^2}$ orbitals degrades superconductivity, $T_c$ can still be high enough to understand the experiment thanks to the very high $T_c$ reached in the bilayer Hubbard model.